Method for forming fluorinated ionomers

Abstract

This invention concerns a method for forming ionomers by treatment with ammonium carbonate of copolymers having a substantially fluorinated, but not perfluorinated, polyethylene backbone having pendant groups of fluoroalkoxy sulfonyl fluoride. Ionomers derived therefrom by ion exchange are useful in electrochemical applications such as batteries, fuel cells, electrolysis cells, ion exchange membranes, sensors, electrochemical capacitors, and modified electrodes.

1. An ionomer comprising monomer units of vinylidene fluoride and 0.5–50 mole % of a perfluoroalkenyl monomer having a pendant group of the formula
   —(O—CF 2 CFR) a O—CF 2 (CFR′) b SO 3   − NH 4   +   
 
       wherein R and R′ are independently selected from F, Cl or a perfluorinated alkyl group having 1 to 10 carbon atoms, a=0, 1 or 2, b=0 to 6. 
     
     
       2. The ionomer of  claim 1  in the form of a flat film or sheet. 
     
     
       3. The ionomer of  claim 1  comprising 0.5–36 mole % of said perfluoroalkenyl monomer having a pendant group. 
     
     
       4. The ionomer of  claim 1  wherein a=1, b=1, R is trifluoromethyl, and R′ is fluorine.